<!doctype html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>Document</title>
	<style type="text/css">
	*{ box-sizing:border-box; }
	#box{ margin:50px;
		 width:200px;
		 height:100px;
		 background: red;
		 animation:aa 5s;
		 animation-timing-funciton:ease-in-out;
		}
	@keyframes aa{
		from{width:200px; }
		to{width:800px;}
	}

	</style>
</head>
<body>
	<div id="box">		
	</div>
</body>
</html>
